1. Field of the Invention
The present invention is directed to a method of making a mold for replication of a part or article from a design, and in particular, the method includes making a model of the part from the design and creating a mold of the part from the model, and thereafter making a part in the mold.
2. Description of the Prior Art
Generally numerous methods are known for making a mold from a three-dimensional model of a part design. For example, in the shoe manufacturing industry, a shoe part, for example a shoe midsole, is typically first designed or drawn on paper in a two-dimensional format and then typically made into a three-dimensional model. Shoe midsoles have an outside peripheral surface which is normally contoured and detailed and which has various areas of surface texturing, for example, stippling or raised ribs. The three-dimensional model made of a midsole design typically has the general shape of the midsole but does not normally have the surface texturing applied thereto, the surface texturing comprising an important part of the midsole design. The midsole model without surface texturing is then typically used to create a master mold. With reference to FIGS. 23 and 24, prior art master mold 20 typically has two separable members 22 and 24 and is typically made out of a metal, for example, aluminum or steel. Members 22 and 24 are separated along parting line 26 and share an aperture 28 partly disposed in each of the members. As best shown in FIG. 24, aperture 28 has inner peripheral surface 30. Inner peripheral surface 30 has contoured portion 32 which is an impression of the contoured outer peripheral surface of the shoe midsole model. However, this impression typically does not exhibit the surface texturing that is part of the midsole design.
Mold members 22 and 24 are bolted together by fastening bolt 34. Master mold 20 typically has upper mold plate 36 and lower mold plate 38. Lower mold plate 38 has mold protrusion 40 with upper surface 42 which has an impression corresponding to the lower surface of the midsole model. Mold protrusion 40 has the same general perimeter shape as the midsole model. When lower mold plate 38 is positioned on the bottom surfaces of mold members 22 and 24 as indicated by the arrows in FIG. 24, mold protrusion 40 fills the portion of aperture 28 below the contoured portion 32 of inner peripheral surface 30. Upper mold plate 36 has mold protrusion 44 with bottom surface 46 which has an impression corresponding to the upper surface of the midsole model. Mold protrusion 44 has a perimeter shape that corresponds to the perimeter shape of the midsole model. When upper mold plate 36 is positioned on the upper surface of mold members 22 and 24 as indicated by the arrows in FIG. 24, protrusion 44 is positioned such that it fills the portion of aperture 28 above contoured portion 32 of inner peripheral surface 30. Thus, when lower mold plate 38 and upper plate 36 are positioned on mold members 22 and 24, an inner space is created which replicates the midsole model. After master mold 20 has been made from the midsole model, the midsole model is typically discarded or put into storage.
Duplicates models which replicate the midsole model are now made using master mold 20. The duplicates are typically made out of a plaster material. Generally, master mold members 22 and 24 are bolted together and lower mold plate 38 is positioned on the bottom thereof. Plaster in its liquid form is then poured into aperture 28. Thereafter, upper mold plate 36 is positioned on top of mold members 22 and 24. The plaster is then allowed to solidify such that a plaster duplicate of the midsole model is made. The plaster duplicate is removed from master mold 20 by removing upper and lower mold plates 36 and 38 and by loosening bolts 34 such that mold members 22 and 24 can be separated to release the plaster duplicate.
Because of parting line 26 between mold members 22 and 24, a plaster duplicate produced from master mold 20 will have a flash line on its forward end and its rearward end corresponding to where part line 26 intersects aperture 28. These flash lines on the plaster duplicate must be removed before the plaster duplicate can be used to make a production mold for the finished shoe midsole. Typically, numerous plaster duplicates are created using master mold 20. On each of the duplicates created the flash lines on the forward and rearward ends must be removed. Such removal typically is done by hand and thus is relatively time consuming and expensive. Further, if a metal master mold is made to include impressions of surface texturing on its molding surface such that a plaster duplicate made from the master mold has surface texturing thereon, the removal of the flash lines from the plaster duplicate likely will damage the surface texturing on the duplicate (especially in the areas of the flash lines), thus, requiring reworking or reapplying of the surface texturing to the duplicate. Additionally, in a metal master mold made with impressions of surface texturing, the intricately detailed surface texturing of a plaster duplicate formed thereon can be damaged by the unyielding metal master mold when the duplicate is removed from metal master mold.
Once a number of plaster duplicates have been made from master mold 20, the duplicates are then used to make a number of production molds for manufacturing finished midsoles. The number of production molds of the midsole design needed depends upon the number of parts to be manufactured and the speed with which they must be produced. Typically, the plaster duplicates are used to make cast aluminum molds of the midsole design. That is, the plaster duplicates are encased in molten aluminum which is allowed to harden, and thereafter, the plaster duplicate is destroyed such that all that remains is the aluminum production mold with a mold impression left by the plaster duplicate, the mold impression corresponding to the midsole design.
As described above, the midsole model, and thus the plaster duplicates made therefrom, typically do not reflect the surface texturing of the midsole design. Therefore, surface texturing needs to be added to each of the aluminum production molds made from the plaster duplicates. The surface texturing is typically applied manually, and thus, is labor intensive and costly and leads to each aluminum mold being slightly different from the others. Therefore, depending upon which production mold a shoe part is manufactured from, the surface texturing may be slightly different from midsole to midsole.
Typically, ethylene vinyl acetate (EVA) or polyurethane (PU) is poured into the aluminum production molds to make the final shoe midsole.
The prior art method described above requires the labor intensive removal of the flash lines from the plaster duplicates. Further, the method produces production molds which are all slightly different from the other because of the surface texturing being applied to each mold individually by hand.
The use of an elastomeric or resilient material as a part or portion of a mold is generally known. In aluminum production molds used to make shoe midsoles, resilient mold parts are sometimes used to isolate a structure to be imbedded in the midsole to prevent the EVA or PU from covering the structure such that the structure is allowed to be visible along the outer peripheral surface of the midsole. For example, an elastomeric gasket is sometimes used to protect a transparent air bladder such that portions of the transparent bladder are visible along the periphery of the midsole after the midsole has been formed. The elastomeric gasket is positioned along a portion of the molding surface of the aluminum production mold such that it tightly engages portions of the transparent bladder to prevent liquid EVA or PU from seeping therebetween, and thus, allowing the portions of the bladder engaged by the gasket to be visible along the periphery of the finished midsole.
Still furthermore, U.S. Pat. No. 3,838,956; European Patent No. 0,273,028; and Austrian Patent No. 353,142 all disclose the use of an elastomeric mold part for preventing a flash line on the rear or heel end of a finished shoe sole. These references appear to generally disclose the forming of a shoe sole on a shoe upper using an injection molding process and the use of an elastomeric mold member to prevent a flash line on the rear of the sole of the finished shoe. U.S. Pat. No. 3,504,079 discloses using an elastomeric material to make a mold for a shoe sole such that the mold can be used to form a shoe sole on an upper. The elastomeric properties of the material allow the entire finished shoe to be removed from the mold. U.S. Pat. No. 3,974,996 discloses a method of making a final production mold for the contoured outer surface of a candle by encasing a candle mandrel in a shell and pouring an elastomeric material in an annular space formed between the mandrel and the shell. The patent discloses that the mold-making process can be used for devices having varying and/or otherwise irregular cross sections.
All of the above references generally disclose the use of an elastomeric mold part in a final or production mold used to produce the actual manufactured article. As is apparent, when hundreds or thousands of articles are produced using production molds with elastomeric parts, the elastomeric parts of the mold may deteriorate, and thus, result in inconsistencies and defects in the manufactured articles or parts. Further, elastomeric mold parts in production molds can be unsuitable to resist the heat and pressure required for molding many articles or parts. Further, if numerous molds are required to increase the rate of manufacturing articles or parts, final production molds using elastomeric parts may be unacceptable because of the complexity and cost of producing such molds.